As the use of mobile wireless devices, such as smart phones and tablet devices, becomes more ubiquitous, the demands on the limited amount of radio frequency spectrum used by those devices also increases, resulting in wireless network congestion in the licensed spectrum. In addition, the increased use of high bandwidth applications such as audio and video streaming can increase demands beyond the capability of the available spectrum. This is especially true in high density and high use locations such as large cities and universities. One projection estimates a growth of 20 times in mobile internet traffic from 2010 to 2015.
One way of increasing bandwidth in wireless devices is through the use of heterogeneous wireless networks (HetNet), in which multiple nodes are co-located to provide increased data throughput to mobile devices communicating with one or more nodes within a cell. A cell is typically defined as the geographic area over which a macro base station, such as an enhanced Node B (eNode B) is configured to communicate with a mobile device. A macro base station can be one node located within the cell. Additional low power nodes can also be located in a cell.
A cell is often depicted as a circular area with a predefined radius. However, the actual shape of radiation patterns for antennas in a base station can differ from the predefined radius. Moreover, the use of beam forming and/or Multiple-Input Multiple-Output (MIMO) systems enables a cell to communicate at distances greater than a typical predefined radius in certain instances. The actual radiation pattern of a base station antenna can result in areas within the cell that have relatively low signal strength which can result in slow data connections and dropped phone calls.
Low power nodes in the HetNet can be used to provide access to mobile devices located in areas having low signal strength. In addition, low power nodes can also be used to increase the density of mobile device communication in a defined area.
However, transmitting and receiving over different paths can create a number of challenges. For example, signals communicated from mobile devices may travel different paths between the wireless device and the nodes located within a cell. The distinct propagation paths between different carriers can create timing differences in the reception of the signals. This can be disadvantageous in wireless systems that combine data for multiple devices in a single signal, such as in systems that use Orthogonal Frequency Division Multiple Access (OFDMA).
Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.